Poor oral health is concentrated in adults living with HIV, and periodontal disease is currently the most common oral health problem related to HIV. In the United States, nearly 50% of all adults over age 30 have periodontal disease. Oral health and general health are intimately linked. A greater emphasis on preventing and managing periodontal disease is an urgent public health priority. Applying an established, well-tested health behavior theory, the Information- Motivation-Behavioral Skills (IMB) Model, could be highly effective in reducing risk for periodontal disease and poor health outcomes in HIV+ adults. Interventions to enhance preventative behaviors in HIV+ adults would likely generalize to other populations with similar but fewer risk factors for periodontal disease. Managing gum disease is based on excellent plaque control and ongoing dental treatment; clinically, we have early evidence that when HIV+ adults are aware of their level of periodontal disease and are coached to master specific oral hygiene skills to reduce their risk (i.e. improved tooth brushing and flossing), they become more engaged in the process and demonstrate greater motivation to initiate and maintain self-care behaviors. Our long-term goal is to apply well-established health behavior theory (i.e., the IMB Model) to test our clinical finding in a rigorous, evidence-based manner. To reach that goal, we first need an observable measure of these skills (i.e., tooth brushing and flossing), since current measures used in dentistry are only indirect measures of oral hygiene skill mastery. Therefore, our Primary Aim in this application is to finalize and evaluate the psychometric properties of a provider-observed Oral Hygiene Skills Mastery (OHSIM) in a cohort of at-risk HIV+ adults (total N=123). Objective A is to finalize development of the OHSIM including a Coder's Manual and scoring algorithms for each of the two components (i.e., tooth brushing and flossing skill) as well as an overall composite score. Objective B is to establish methods for training coders and evaluate inter-rater agreement (and internal consistency) for each component measure of the OHSIM. Objective C is to assess concurrent validity by examining correlations between OHSIM components and the overall composite score against established dental outcome measures: the modified Quigley-Hein plaque index (QHI), periodontal probing depth (PPD), gingival recession (REC), clinical attachment level (CAL) and bleeding on probing (BOP), controlling for relevant demographics and oral health covariates. Development of a valid and reliable OHSIM will enable rigorous, evidenced-based behavioral oral health research that may help promote a greater emphasis on prevention in dentistry for at risk groups.